org-src: Fix docstring

* lisp/org-src.el (org-src-ask-before-returning-to-edit-buffer): Fix
  docstring.  Move variable in appropriate section.

lisp/org-src.el

@@ -124,6 +124,17 @@ first line of the window showing the editing buffer."
   :group 'org-edit-structure
   :type 'boolean)
 
+(defcustom org-src-ask-before-returning-to-edit-buffer t
+  "Non-nil means ask before switching to an existing edit buffer.
+If nil, when `org-edit-src-code' is used on a block that already
+has an active edit buffer, it will switch to that edit buffer
+immediately; otherwise it will ask whether you want to return to
+the existing edit buffer."
+  :group 'org-edit-structure
+  :version "24.4"
+  :package-version '(Org . "8.0")
+  :type 'boolean)
+
 (defcustom org-src-window-setup 'reorganize-frame
   "How the source code edit buffer should be displayed.
 Possible values for this option are:
@@ -511,16 +522,6 @@ with \",*\", \",#+\", \",,*\" and \",,#+\"."
 (define-key org-src-mode-map "\C-c\C-k" 'org-edit-src-abort)
 (define-key org-src-mode-map "\C-x\C-s" 'org-edit-src-save)
 
-(defcustom org-src-ask-before-returning-to-edit-buffer t
-  "If nil, when org-edit-src code is used on a block that already
-has an active edit buffer, it will switch to that edit buffer
-immediately; otherwise it will ask whether you want to return to
-the existing edit buffer."
-  :group 'org-edit-structure
-  :version "24.4"
-  :package-version '(Org . "8.0")
-  :type 'boolean)
-
 (define-minor-mode org-src-mode
   "Minor mode for language major mode buffers generated by org.
 This minor mode is turned on in two situations: